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Ethics approval was obtained from the Institutional Review Board of the University of Hong Kong/Hospital Authority Hong Kong West Cluster (HKU/HA HKW IRB) (reference number: UW 16–102) and Hospital Authority Kowloon West Cluster Research Ethics Committee (reference number: KW/EX-17-028(108–07)).The information sheet states the purpose and nature of the study, potential benefits and risks of participating in the study, and that individual information collected will be kept anonymous and strictly confidential. Participants may decide whether or not to participate and they may withdraw anytime with no negative consequences. Consent to participate was obtained by participants sending back a completed survey.